Mineral fiber-insulating webs are normally hitherto produced as homogeneous webs, i.e. webs in which the mineral fibers of which the mineral fiber-insulating web is composed, are generally orientated in a single predominant orientation which is determined by the orientation of the production line on which the mineral fiber-insulating web is produced and transmitted during the process of producing the mineral fiber-insulating web. The product made from a homogeneous mineral fiber-insulating web exhibits characteristics which are determined by the integrity of the mineral fiber-insulating web and which are predominantly determined by the binding of the mineral fibers within the mineral fiber-insulating plate produced from the mineral fiber-insulating web, and further predominantly determined by the area weight or density of the mineral fibers of the mineral fiber-insulating plate.
The advantageous characteristics of mineral fiber-insulating plates of a different structure has to some extent already been realized as techniques for the production of mineral fiber-insulating plates in which the mineral fibers are orientated in an overall orientation different from the orientation determined by the production line, has been devised, vide Published International Patent Application, International Application No. PCT/DK91/00383, International Publication No. WO92/10602, U.S. Pat. No. 4,950,355, Published International Patent Application, International Application No. PCT/DK87/00082, International Publication No. WO88/00265, French Patent No. 938294, U.S. Pat. No. 3,230,955 and Swedish Patent No. 452.040. Reference is made to the above patent applications and patents, and the above U.S. patents are hereby incorporated in the present specification by reference.
From the above published international patent application, International Publication No. WO92/10602, a method of producing an insulating mineral fiber plate composed of interconnected rod-shaped mineral fiber elements is known. The method includes cutting a continuous mineral fiber web in the longitudinal direction thereof in order to form lamellae, cutting the lamellae into desired lengths, turning the lamellae 90.degree. about the longitudinal axis and bonding the lamellae together for forming the plate. The method also includes a step of curing the continuous mineral fiber web, or alternatively the plate composed of the individual lengths of lamellae bonded together for the formation of the plate.
From the above-mentioned published international patent application, International Publication No. WO88/00255, a method of folding a continuous mineral fiber web in a transversal direction relative to the longitudinal direction of the mineral fiber web is known for the formation of an undulated mineral fiber web. Dependent of the origin of the mineral fiber web from which the undulated mineral fiber web is produced, the undulated mineral fiber web may include mineral fibers orientated along the undulations or perpendicular to the undulations.
From French patent No. 938294 and U.S. Pat. No. 3,230,995, techniques of producing mineral fiber boards or plates composed of rod-shaped elements are known, which techniques are similar to the technique described in the above first-mentioned international patent application. Thus, according to the techniques described in the above French and U.S. patents, a board or plate of a mineral fiber material is cut into lengths of rod-shaped elements which are thereupon turned and reassembled into a composite rod-shaped mineral fiber plate structure. These well-known prior art techniques involve a separate step of bonding the rod-shaped lamellae together by means of an appropriate bonding agent or foamed agent as described in the above-mentioned U.S. patent.